Abstract: Inside thermal screen is an efficient way to conserve energy in the heating systems of agricultural greenhouses. Reflective thermal screen with aluminum is now popolar, because of outstanding effectiveness in increasing energy conservation and the convenience with which it can be implemented. The objective of this paper is to do some theoretical analysis and calculation on the energy conservation rate of inside thermal screen. The heat preservation mechanism of thermal screen was discussed, and a mathematical model to calculate the energy conservation effect of employing thermal screen in agricultural greenhouses was built. The results of the calculation showed the influence of radiative qualities on energy conservation. It addition, some experiments were conducted to validate the results.